Embolic management filter design

ABSTRACT

Embolic protection filter assembly and method of using the same. In some embodiments, the present invention comprises an embolic protection filter slidably disposed over an elongate shaft.

FIELD OF THE INVENTION

[0001] The present invention pertains to devices for filtering debris from a body lumen. More particularly, the present invention pertains to devices for filtering embolic debris that is generated by intravascular intervention.

DESCRIPTION OF THE RELATED ART

[0002] Heart and vascular disease are majors problem in the United States and throughout the world. Conditions such as atherosclerosis result in blood vessels becoming blocked or narrowed. This blockage can result in lack of oxygenation of the heart, which has significant consequences since the heart muscle must be well oxygenated in order to maintain its blood pumping action.

[0003] Occluded, stenotic, or narrowed blood vessels may be treated with a number of relatively non-invasive medical procedures including percutaneous transluminal angioplasty (PTA), percutaneous transluminal coronary angioplasty (PTCA), and atherectomy. Angioplasty techniques typically involve the use of a balloon catheter. The balloon catheter is advanced over a guidewire such that the balloon is positioned adjacent a stenotic lesion. The balloon is then inflated and the restriction of the vessel is opened. During an atherectomy procedure, the stenotic lesion may be mechanically cut away from the blood vessel wall using an atherectomy catheter.

[0004] During angioplasty and atherectomy procedures, embolic debris can be separated from the wall of the blood vessel. If this debris enters the circulatory system, it could block other vascular regions including the neural and pulmonary vasculature. During angioplasty procedures, stenotic debris may also break loose due to manipulation of the blood vessel. Because of this debris, a number of devices, termed embolic protection devices, have been developed to filter out this debris.

BRIEF SUMMARY OF THE INVENTION

[0005] The present invention relates to embolic protection filters. In some embodiments, the present invention includes an embolic protection filter assembly. The assembly may include a filter coupled to an elongate shaft. The filter may include a number of features. For example, the filter may also include or otherwise be coupled with a distal tip. In some embodiments, the filter (together with the distal the tip) may be slidable over the shaft.

[0006] The filter may be delivered to an appropriate location (e.g., adjacent a lesion within a blood vessel) with a delivery catheter. In some embodiments, the filter may be self-expanding so that retracting the delivery catheter from the filter results in the filter expanding. An aspiration tube or other suitable aspiration means may be used to aspirate embolic debris from the filter at any time during the filtering procedure. Upon completing of the intervention, a retrieval catheter or other suitable means may be used to retrieve the filter.

BRIEF DESCRIPTION OF THE DRAWINGS

[0007]FIG. 1 is a partial cross-sectional view of an embodiment of an embolic protection filter assembly;

[0008]FIG. 2 is a partial cross-sectional view of an embodiment of an embolic protection filter assembly, wherein the filter is collapsed within a delivery catheter;

[0009]FIG. 3 is a perspective view of an embodiment of a support member for use with an embolic protection filter assembly;

[0010]FIG. 4 is a partial cross-sectional view of an alternate embodiment of an embolic protection filter assembly;

[0011]FIG. 5 is a partial cross-sectional view of an embolic protection filter assembly including an aspiration tube;

[0012]FIG. 6 is a partial cross-sectional view of an embolic protection filter assembly including an alternative aspiration tube;

[0013]FIG. 7 is a partial cross-sectional view of an embolic protection filter assembly wherein an aspiration tube is advanced over the filter, prolapsing the filter;

[0014]FIG. 8 is a partial cross-sectional view of an embolic protection filter assembly wherein the filter includes a strut;

[0015]FIG. 9 is a partial cross-sectional view of another example embolic protection filter assembly that includes a strut;

[0016]FIG. 10 is a partial cross-sectional view of an embolic protection filter assembly partially collapsed;

[0017]FIG. 11 is a partial cross-sectional view of an embolic protection filter assembly partially collapsed;

[0018]FIG. 12 is a partial cross-sectional view of an embolic protection filter assembly wherein the filter includes more than one strut;

[0019]FIG. 13 is a partial cross-sectional view of another example embolic protection filter assembly;

[0020]FIG. 14 is a partial cross-sectional view of an embolic protection filter assembly collapsed;

[0021]FIG. 15 is a partial cross-sectional view of an embolic protection filter assembly collapsed and disposed within a retrieval sheath;

[0022]FIG. 16 is a partial cross-sectional view of an embolic protection filter assembly;

[0023]FIG. 17 is a partial cross-sectional view of another example embolic protection filter assembly;

[0024]FIG. 18 is a partial cross-sectional view of an embolic protection filter assembly collapsed;

[0025]FIG. 19 is a partial cross-sectional view of an embolic protection filter assembly wherein the filter includes pull cord for collapsing the filter;

[0026]FIG. 20 is a partial cross-sectional view of an embolic protection filter assembly wherein the pull cord is actuated and the filter is partially collapsed; and

[0027]FIG. 21 is a partial cross-sectional view of an embolic protection filter assembly wherein an alternative pull cord is actuated and the filter is partially collapsed.

DETAILED DESCRIPTION

[0028] The following description should be read with reference to the drawings wherein like reference numerals indicate like elements throughout the several views. The detailed description and drawings illustrate example embodiments of the claimed invention.

[0029]FIG. 1 is a partial cross-sectional view of an embodiment of an embolic protection filter assembly 10. Assembly 10 includes an embolic protection filter 12 coupled to an elongate shaft 14. Filter 12 includes an expandable support member 18. Support member 18 may be adapted and configured to shift filter 12 between a first generally collapsed configuration and a second generally expanded configuration to define an open filler month.

[0030] Filter 12 may be comprised of a polyurethane nylon sheet, silicone filter or other suitable material. In some embodiments, the filter material may be injection molded over support member 18. The filter material includes at least one opening that may be, for example, formed by laser techniques. The holes or openings are sized to allow blood flow therethrough but restrict flow of debris or emboli floating in the body lumen or cavity. As stated above, filter 12 is adapted to shift between a collapsed configuration and an expanded configuration. In general, the collapsed configuration is appropriate for advancing filter 12 through the vasculature and the expanded configuration is appropriate for collecting debris from the vasculature.

[0031] Filter 12 may include distal portion 20 and an enlarged proximal portion 22. Distal portion 20 may be generally tapered. Additionally, filter 12 may include a tapered tip or nose cone 24. Proximal portion may be enlarged so as to increase the filtering capacity of filter 12. Filtering capacity is defined as the amount of embolic material that filter 12 can capture before becoming saturated. This feature may allow multiple embodiments of filter 12 to be constructed that have different filtering capacities.

[0032] As stated above, filter 12 may include or otherwise be coupled with tip 24. Tip 24 generally includes a tapered distal region 26 and a proximal region 28 that is coupled to or directly connected to filter 12. Distal region 26 is configured so that when filter 12 is disposed within a delivery catheter 30, the tapered distal region 26 extends from a distal end 32 of delivery catheter 30 to provide it with an atraumatic tip (please see FIG. 2). It can be appreciated that catheter 30 may comprise any number of catheters (diagnostic, therapeutic, or guide) as well as other medical devices and should not be limited to a “delivery” catheter.

[0033] In some embodiments, tip 24 is generally tubular and adapted to be slidable over shaft 14. According to this embodiment, filter 12 is connected to tip 24 so that filter 12 can be advanced or “slid” over shaft 14. A number of methods may be used to advance filter 12 over shaft 14. For example, filter 12 may be disposed within delivery catheter 30 and advanced (along with delivery catheter 30) over shaft 14. In this embodiment, filter 12 may have a greater coefficient of friction with delivery catheter 30 than with shaft 14 so that both filter 12 and delivery catheter 30 can be advanced over shaft 14 without filter 12 significantly shifting its position within catheter 30. Alternatively, a pusher or other appropriate physical means may be used to advance filter 12 and tip 24 over shaft 14.

[0034] Upon reaching a desired location along shaft 14, it is important to be able to remove delivery catheter 30 so that filter 12 may be delivered (i.e., expanded to essentially appose the blood vessel). In some embodiments, assembly 10 may include a distal stop 34 coupled to shaft 14. Distal stop 34 is sized so that tip 24 may be passed over a portion of stop 34 and then be friction fit thereto. To allow delivery catheter 34 to be removed, it may be beneficial for the coefficient of friction between tip 24 and stop 34 to be greater than that between tip 24 and delivery catheter 30. Thus, tip 24 can fit tightly enough with stop 34 so that catheter 30 can be retracted without significantly altering the position of filter 12.

[0035] Additionally, shaft 14 may include a proximal stop 35. Proximal stop 35 is generally tapered (e.g., becomes larger in the distal direction) and allows assembly 10 to pass over (in the distal direction) but limit the ability of assembly 10 to pass back over in the proximal direction. Proximal stop 35 may be used in conjunction with distal stop 34 to define a specific target region along shaft 14 where filter 12 can be disposed. Moreover, proximal stop 35 may also be useful for holding filter 12 in position when retracting catheter 30.

[0036] The feature of tip 24 being generally tubular allows filter assembly 10 be used with essentially any shaft 14. For example shaft 14 may comprise a guidewire, catheter (e.g., a guide, diagnostic, or therapeutic catheter), or other similar medical device. Thus, tip 24 can make assembly 10 very flexible in terms of its utility with a number of differing devices and interventions.

[0037]FIG. 2 is a partial cross-sectional view of assembly 10, wherein filter 12 is collapsed within delivery catheter 30. The configuration shown in FIG. 2 is appropriate for advancing assembly 10 through the vasculature (or other body lumen). As can be seen, assembly 10 can be coupled to delivery catheter 30 such that filter 12 assumes the collapsed configuration within catheter 30 (e.g., by back-loading filter 12 into catheter 30). Also, tip 24 can be configured such that distal region 26 extends from distal end 32 of catheter 30, thus providing an atraumatic tip to assembly 10.

[0038] In use, filter 12 (as well as tip 24 and catheter 30) can be advanced over shaft 14 to an area of interest. In some embodiments, filter 12 is advanced distally until tip 24 becomes friction fit or otherwise coupled to stop 34 as described above. Once assembly 10 is advanced to the desired location, catheter 30 can be withdrawn proximally from filter 12 and tip 24. Withdrawing catheter 30 allows filter 12 to shift to the expanded configuration (e.g., by allowing support member 18 to self-expand).

[0039]FIG. 3 is a perspective view of an embodiment of support member 18, apart from filter 12. Support member 18 may comprise a ring or loop. In some embodiments, it may be useful to incorporate the property of super-elasticity into support member 18. For example, support member 18 may be comprised of a shape-memory and/or super-elastic alloy such as nickel-titanium alloy. The super-elasticity and/or shape memory properties can be used to bias support member into the (second) expanded configuration. Thus, support member 18 will cause filter 12 to self-expand when becoming unconfined by, for example, catheter 30.

[0040] A coil or wire 36 may be disposed about support member 18. In some embodiments, wire 36 may be comprised of or include a coating or plating of radiopaque material. Radiopaque materials are understood to be materials capable of producing a relatively bright image on a fluoroscopy screen or another imaging technique during a medical procedure. This relatively bright image aids the user of assembly 10 (and filter 12) in determining its location. Radiopaque materials can include, but not limited to, gold, platinum, palladium, tantalum, tungsten alloy, plastic material loaded with a radiopaque filler, etc.

[0041]FIG. 4 is a partial cross-sectional view of an alternate embodiment of embolic protection filter assembly 110. Assembly 110 is essentially the same in form and function as assembly 10 except that filter 112 includes a narrow proximal portion 138 in addition to distal portion 120 and enlarged proximal portion 122. Because embolic debris can tend to accumulate near distal portion 120, it may be desirable to increase the filtering capacity of distal portion 120. Narrow proximal portion 138 accomplishes this by providing additional surface area to distal portion 120. Thus, narrow proximal portion 138 may be described as being an extension of distal portion 120. In some embodiments, narrow proximal portion 138 extends proximally of portion 122. It can be appreciated that the length of narrow proximal portion 138 can be altered to suit multiple embodiments without departing from the scope of the invention.

[0042] Narrow proximal portion 138 may also include a support member (not shown) that functions essentially the same as support member 18. According to this embodiment, narrow proximal portion 138 can be adapted to shift between expanded and collapsed configurations. Alternatively, narrow proximal portion 138 may include an expanding frame or be otherwise self-expanding.

[0043] For several reasons, it may be desirable to aspirate captured embolic debris from filter 12 during an intervention. For example, filter 12 may become saturated with debris and begin to occlude blood flow through a blood vessel. FIG. 5 is a partial cross-sectional view of embolic protection filter assembly 10 further comprising an aspiration tube 40. Aspiration tube 40 includes an aspiration lumen 42 and a distal end 44. Aspiration tube 40 may advanced, for example through catheter 30, to a location near filter 12. Application of a vacuum to aspiration tube 40 allows debris to be aspirated from filter 12 through lumen 42.

[0044] Aspiration tube 40 may be used by advancing it within catheter 30 (e.g., through a lumen within catheter 30) until distal end 44 is at least partially disposed adjacent filter 12. In some embodiments, distal end 44 extends within a substantial portion of filter 12 so that embolic debris can be aspirated from a significant portion thereof.

[0045]FIG. 5 also illustrates that catheter 30 may include a port 46 adapted to allow single-operator-exchanges of medical devices over shaft 14. This feature may be essentially the same as other analogous single-operator-exchange medical devices.

[0046]FIG. 6 is a partial cross-sectional view of embolic protection filter assembly 10 further comprising an alternative aspiration tube 48. Tube 48 is essentially the same in form and function as tube 40 and includes an aspiration lumen 50 and a distal end 52. In some embodiments, tube 48 is delivery catheter 30 or can be used in place of catheter 30. Alternatively, tube 48 can be advanced over shaft 14 independently of delivery catheter 30.

[0047] After an intervention is complete, assembly 10 can be retrieved from the vasculature. FIG. 7 illustrates an embodiment suitable for retrieval wherein a tube 52 is advanced over filter 12, prolapsing filter 12. Tube 52 may comprise a retrieval catheter, an aspiration tube (e.g., tube 40 or 48), delivery catheter 30, or any other suitable tube.

[0048] Tube 52 can be advanced over shaft 14 in the distal direction until encountering filter 12. Tube 52 can then be further advanced so as to prolapse filter 12. When prolapsed, filter 12 generally becomes disposed over proximal portion 28 of tip 24. Tube 52 can then be advanced over filter 12. Prolapsing filter 12 places filter 12 in a collapsed configuration suitable for removal from the vasculature. Because filter 12 may contain embolic debris and because prolapsing filter 12 may cause the debris to disassociate from filter 12, it may be beneficial to apply a vacuum to tube 52 in order to aspirate debris from filter 12 before, during, and after prolapsing filter 12.

[0049]FIG. 8 is a partial cross-sectional view of embolic protection filter assembly 210. Assembly 210 is essentially the same in form and function as assembly 10, except that filter 212 includes a strut 256 extending between proximal portion 222 and shaft 14. Filter 212 is essentially the same as filter 12 and includes distal portion 220. Strut 256 may allow a catheter or other retrieval device (e.g., catheter 30) to at least partially collapse filter 212 so that it may be disposed within the retrieval catheter. For example, when distal end 32 of catheter 30 is moved in the distal direction distal end 32 may engage strut 256. The result of this engagement is filter 212 tending to shift to the collapsed configuration.

[0050]FIG. 9 is a partial cross-sectional view of another example embolic protection filter assembly 710 that illustrates that strut 756, in addition to being coupled to shaft 14, could also be coupled to tip 724. Assembly 710 is essentially the same in form and function as assembly 210 except that proximal portion 728 of tip 724 extends proximally of filter 712 and strut 756 is coupled to proximal portion 728.

[0051]FIG. 10 is a partial cross-sectional view of embolic protection filter assembly 710 partially collapsed for retrieval from a body lumen. As sheath 30 is advanced over shaft 14, it engages strut 756. This engagement causes strut 756 to shift in position and begin to shift filter 712 from the expanded configuration toward the collapsed configuration. Further advancement of sheath 30 results in further collapsing of filter 712 as shown in FIG. 11 and, eventually, the substantial (and/or complete) containment of filter 712 within sheath 30 (see, for example, FIG. 7).

[0052] Similar to FIGS. 8-11, FIG. 12 illustrates embolic protection filter assembly 310 having more than one strut 356 extending between filter 312 and shaft 14. Filter 312 is essentially the same as filter 12 and includes distal portion 320 and proximal portion 322. Struts 356 function essentially the same as struts 256 and, thus, may be used to collapse and/or retrieve filter 312. It can be appreciated that struts 356 could also be coupled to other parts of assembly 310.

[0053]FIG. 13 is a partial cross-sectional view of another example embolic protection filter assembly 810. Assembly 810 is essentially the same in form and function as other assemblies described herein except that it includes an expandable tip 824. Expandable tip 824 is configured so that at least a portion thereof can shift between a generally collapsed configuration (as best seen in FIG. 13) and a generally expanded configuration (as best seen in FIGS. 14 and 15). When tip 824 is expanded, filter 812 may become at least partially collapsed and disposed therein. Thus, expandable tip 824 may be used to aid retrieval of filter 812.

[0054]FIG. 14 is a partial cross-sectional view of embolic protection filter assembly 810 with tip 824 in a generally expanded configuration and with filter 812 disposed within tip 824. In order for filter 812 to become disposed within tip 824, sheath 30, for example, may be advanced over shaft 14 to a position adjacent filter 812. Sheath 30 can then be further advanced distally so that it contacts and exerts a force upon filter 812 that is sufficient to slide filter 812 into tip 824. It can be appreciated that other devices may be used to shift filter 812 so that it becomes disposed within tip 824. For example, a pusher tube may be advanced over shaft 14 or within sheath 30 may be used. Additionally, filter 812 may included a reinforced pushing surface that is configured to provide structural support at the point of contact between sheath 30 and filter 812. This surface may be defined by a larger or stronger portion of filter 812, a subassembly disposed adjacent filter 812, a part of the filter frame, and the like.

[0055] To assist the shifting of filter 812 between the expanded configuration and the collapsed configuration, tip 824 may include a longitudinal portion 866 and a slidable subassembly 868. Subassembly 868 is connected to filter 812 and may comprise a tube slidably disposed about longitudinal portion 866. According to this embodiment, as filter 812 is shifted distally, subassembly 868 shifts distally along longitudinal portion 866 and filter 812 becomes disposed within tip 824.

[0056] As filter 812 becomes at least partially disposed within tip 824, sheath 30 may be advanced distally toward tip 824 so that a proximal bent portion 870 thereof becomes disposed within sheath 30 as shown in FIG. 15. In this configuration, filter 812 can be removed from the body lumen by retracting shaft 14 and sheath 30.

[0057]FIG. 16 is a partial cross-section view of embolic protection filter assembly 610. Assembly 610 is essentially the same in form and function as assembly 10 except that shaft 614 is tubular and includes one or more aspiration holes 664. In at least some embodiments, shaft 614 has an outside diameter that is comparable to typical guidewires. For example, the outside diameter may be about 0.016 inches or less. Generally, when filter 12 is in a position relative to shaft 614 that is appropriate for filtering embolic debris, holes 664 are located near or within filter 12 so that captured embolic debris may be aspirated through shaft 612.

[0058]FIG. 17 is a partial cross-sectional view of another example embolic protection filter assembly 910 that is essentially the same in form and function as assembly 610, except that it includes an expandable tip 924 that functions essentially the same as tip 824. Similar to what is described above, shaft 914 is tubular and includes one or more aspiration holes 964 that can be used to aspirate embolic debris from filter 912 when a vacuum source is connected to the proximal end of shaft 914.

[0059] Retrieval of filter 912 may include distally advancing sheath 30 (or another suitable structure) along shaft 914 and exerting force upon filter 912 so that filter 912 becomes at least partially disposed within tip 924 as shown in FIG. 18. The mechanism for shifting filter 912 is essentially the same as what is described above and shown in FIGS. 13-15. For example, tip 924 may include longitudinal portion 966 and subassembly 968 and subassembly may slide distally along longitudinal portion 966.

[0060]FIG. 19 is a partial cross-sectional view of embolic protection filter assembly 410. Assembly 410 and filter 412 are essentially the same in form and function as assembly 10 and filter 12, respectively, except that filter 412 includes an engageable ring 458. Engagable ring 458 may be, for example, formed at one end of support member 18 or be connected to a wire or cord disposed about proximal portion 422. Actuating or “pulling” ring 458 results in the circumference of proximal portion 422 becoming smaller. Thus, ring 458 can be used to at least partially collapse filter 412 for retrieval.

[0061] In some embodiments, ring 458 may be actuated by a pull cord 460. Pull cord 460 may extend distally through catheter 30 and extend out of distal end 32 thereof. To engage ring 458, pull cord may include a distal hook 462 adapted and configured to engage ring 458. According to this embodiment, pull cord 462 can be advanced out of distal end 32 of catheter 30, become engaged with ring 458, and be pulled proximally to collapse filter 412. FIG. 20 illustrates assembly 410 with pull cord 462 engaged with ring 458 and pulled proximally to partially collapse filter 412.

[0062]FIG. 21 is a partial cross-sectional view of embolic protection filter assembly 510 having an alternative pull cord 556. Assembly 510 and filter 512 are essentially the same as assembly 10 and filter 12, respectively. Pull cord 556 is connected to proximal portion 522 of filter 512 such that pull cord 556 can be pulled in the proximal direction to collapse filter 512. In some embodiments, pull cord 556 may comprise an extension or be connected to support member 18. Alternatively, pull cord 556 may be generally disposed about proximal portion 522 so that pulling pull cord 556 tightens or shortens the circumference of proximal portion 522 (and generally the circumference of filter 512) so that filter 512 may be retrieved by catheter 30.

[0063] It should be understood that this disclosure is, in many respects, only illustrative. Changes may be made in details, particularly in matters of shape, size, and arrangement of steps without exceeding the scope of the invention. The invention's scope is, of course, defined in the language in which the appended claims are expressed. 

What is claimed is:
 1. A method of making device for filtering embolic debris from a body lumen, comprising the steps of: molding a filter assembly, the filter assembly including a distal tip and a filter portion; forming a plurality of apertures; and coupling a support member to the filter assembly adapted to shift the filter portion between a first generally collapsed configuration and a second generally expanded configuration.
 2. The method in accordance with claim 1, further comprising the step of disposing a distal stop located proximate the distal end of the shaft.
 3. The method in accordance with claim 1, further comprising the step of disposing a proximal stop.
 4. The method in accordance with claim 1, wherein the filter is molded from a filter material comprised of silicon.
 5. The method in accordance with claim 1, wherein the support member is comprised of nickel-titanium alloy.
 6. The method in accordance with claim 1, wherein the support member further comprises a radiopaque coil disposed about at least a portion of the support member.
 7. The method in accordance with claim 1, further comprising the steps of providing an elongate shaft having a proximal end and a distal end, and coupling the filter assembly to the shaft.
 8. The method in accordance with claim 7, wherein the shaft is generally tubular and includes plurality of aspiration holes.
 9. The method in accordance with claim 1, wherein the support member is coupled to the filter assembly by molding the filter assembly to the support member.
 10. The method in accordance with claim 1, further comprising the step of slidably disposing an aspiration tube over the shaft.
 11. The method in accordance with claim 1, wherein the plurality of apertures are formed by laser drilling.
 12. The method in accordance with claim 1, wherein the filter includes one or more struts.
 13. The method in accordance with claim 1, wherein the support member is biased to shift the filter into the second position.
 14. The method in accordance with claim 1, further comprising the step of coupling a ring to the filter assembly.
 15. The method in accordance with claim 14, further comprising the step of providing a pull cord having a distal hook adapted for engaging the ring.
 16. A device for filtering embolic debris from a body lumen, comprising: an elongate shaft having a proximal end and a distal end, the shaft adapted to be slidably disposed within the lumen of the outer tubular member; a filter assembly slidably disposed over the shaft, the filter assembly including a distal tip and a filter; wherein the filter includes a first filter portion and a second filter portion disposed about the first filter portion; and a support loop coupled to the second portion, the loop being adapted to shift the filter between a first generally collapsed configuration and a second generally expanded configuration.
 17. The device in accordance with claim 16, further comprising a distal stop located proximate the distal end of the shaft.
 18. The device in accordance with claim 16, further comprising a proximal stop.
 19. The device in accordance with claim 16, wherein the filter includes a filter material comprised of silicon.
 20. The device in accordance with claim 16, wherein the loop is comprised of nickel-titanium alloy.
 21. The device in accordance with claim 16, wherein the loop further comprises a radiopaque coil disposed about at least a portion of the loop.
 22. The device in accordance with claim 16, further comprising outer tubular slidably disposed over at least a portion of the elongate shaft.
 23. The device in accordance with claim 16, further comprising an aspiration tube slidably disposed over the shaft.
 24. The device in accordance with claim 16, wherein the first portion of filter includes a proximal end that extends proximally of second portion.
 25. The device in accordance with claim 16, wherein the shaft is generally tubular and includes a plurality of aspiration holes proximate the filter.
 26. The device in accordance with claim 16, wherein the filter includes one or more struts.
 27. The device in accordance with claim 16, further comprising a ring coupled to the second portion of the filter.
 28. The device in accordance with claim 27, further comprising a pull cord having a distal hook adapted for engaging the ring.
 29. The device in accordance with claim 16, further comprising a pull cord coupled to the second portion of the filter and extending proximally through a lumen of a tubular catheter.
 30. A method of filtering debris from a body lumen, comprising the steps of: providing an elongate shaft having a proximal end and a distal end; advancing the shaft to a desired location within a body lumen; providing a filter delivery assembly adapted to be slidably disposed about the shaft, the filter delivery assembly including a delivery tube and a filter, the filter including a first portion and a second portion, wherein the first and second portions each include an expandable loop, the loops adapted to shift the filter between a first collapsed configuration when disposed within the delivery tube and a second expanded configuration when the delivery tube is retracted proximally relative to the filter; advancing the filter delivery assembly over the shaft; and retracting the delivery tube proximally relative to the filter to allow the loop to shift to the second configuration.
 31. The method in accordance with claim 30, wherein the elongate shaft includes a distal stop, and wherein the step of advancing the filter delivery assembly over the shaft includes advancing the filter delivery assembly to the distal stop.
 32. The method in accordance with claim 31, wherein the elongate shaft includes a proximal stop, and wherein the step of advancing the filter delivery assembly over the shaft includes advancing the filter distally of the proximal stop.
 33. The method in accordance with claim 30, further comprising the step of aspirating embolic debris from the filter.
 34. The method in accordance with claim 33, wherein the step of aspirating embolic debris includes advancing an aspiration tube over the elongate shaft to a location proximate the first portion of the filter.
 35. The method in accordance with claim 33, wherein the shaft is generally tubular and includes one or more aspiration holes located proximate the filter, and wherein the step of aspirating embolic debris from the filter includes aspirating embolic debris through the aspiration holes.
 36. The method in accordance with claim 30, further comprising the step of retrieving the filter.
 37. The method in accordance with claim 36, wherein the step of retrieving the filter includes advancing a retrieval tube over the shaft and over the filter such that the filter is prolapsed and disposed within the retrieval tube.
 38. The method in accordance with claim 36, wherein the filter includes one or more struts, and wherein the step of retrieving the filter includes advancing a retrieval tube over the shaft such that the struts guide the filter into the retrieval tube.
 39. The method in accordance with claim 36, wherein the filter includes a pull cord coupled to the second portion thereof and extending proximally into a lumen of a retrieval catheter, and wherein the step of retrieving the filter includes actuating the pull cord. 